NEET BIOLOGY

Detailed explanation-1: -A thin-walled sac that surrounds the fetus during pregnancy. The sac is filled with liquid made by the fetus (amniotic fluid) and the membrane that covers the fetal side of the placenta (amnion). This protects the fetus from injury. it also helps to regulate the temperature of the fetus.

Detailed explanation-2: -The inner cells in the thickened area develop into the embryo, and the outer cells burrow into the wall of the uterus and develop into the placenta. The placenta produces several hormones that help maintain the pregnancy.

Detailed explanation-3: -The correct option is B implantation. The zygote formed in the fallopian tube keeps on dividing on its way to the uterus. At this stage, it forms an embryo which attaches to the wall of the uterus. This process is known as implantation.

Detailed explanation-4: -The development of the placenta begins during implantation of the blastocyst. The 32-64 cell blastocyst contains two distinct differentiated embryonic cell types: the outer trophoblast cells and the inner cell mass. The trophoblast cells form the placenta.

Detailed explanation-5: -Specifically, the researchers found that 6 days after an egg is fertilized, the embryo uses specialized molecules on its surface and molecules on the surface of the uterus to attach itself to the wall of the uterus.